| From: | Andrew Gierth <andrew(at)tao11(dot)riddles(dot)org(dot)uk> |
|---|---|
| To: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
| Cc: | Andres Freund <andres(at)anarazel(dot)de>, Colm McHugh <colm(dot)mchugh(at)gmail(dot)com>, pgsql-hackers(at)postgresql(dot)org |
| Subject: | Re: Patch to fix write after end of array in hashed agg initialization |
| Date: | 2019-05-23 10:44:20 |
| Message-ID: | 87woihbgqw.fsf@news-spur.riddles.org.uk |
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| Lists: | pgsql-hackers |
>>>>> "Andrew" == Andrew Gierth <andrew(at)tao11(dot)riddles(dot)org(dot)uk> writes:
Andrew> My inclination is to fix this in the planner rather than the
Andrew> executor; there seems no good reason to actually hash a
Andrew> duplicate column more than once.
I take this back; I don't believe it's possible to eliminate duplicates
in all cases. Consider (a,b) IN (select c,c from...), where a,b,c are
different types; I don't think we can assume that (a=c) and (b=c)
cross-type comparisons will necessarily induce the same hash function on
c, and so we might legitimately need to keep it duplicated.
So I'm going with a simpler method of ensuring the array is adequately
sized at execution time and not touching the planner at all. Draft patch
is attached, will commit it later.
--
Andrew (irc:RhodiumToad)
| Attachment | Content-Type | Size |
|---|---|---|
| hashfix.patch | text/x-patch | 4.2 KB |
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